Extractor for childbirth and aspirator/injector device

ABSTRACT

A medical device which is manually operable to draw a vacuum using a piston and cylinder combination may be used for creating a vacuum in the cup of a birth extraction device or to withdraw fluids from a body cavity or perform biopsies. The structure includes a closed loop at the remote end of the cylinder which allows the device to be manipulated by one hand and it may include check valves to prevent any fluid withdrawn from the body from being reinjected into the body cavity or vessel by location of check valves in a withdrawal duct and a drainage port. The same device may be used for injecting fluids into a body cavity and may include structure between the loop and cylinder to apply force to the piston to discharge fluids through a needle attached to the remote end of the cylinder.

FIELD OF THE INVENTION

This invention relates to a piston and cylinder combination used tocreate a vacuum on a birth cup to assist in the delivery of an infant. Asimilar piston and cylinder structure may be used to withdraw fluidsfrom body cavities, perform needle biopsies of soft tissues and solidorgans, inject substances into the body, or transfer fluids from onevessel to another or otherwise create low volume, high pressure vacuumfor medical or industrial uses.

BACKGROUND OF THE INVENTION

The original concept of this invention arose from difficultiesencountered by one of the inventors in hospital delivery rooms where thestructure and associated apparatus of existing obstetric vacuumextractors for assisting childbirth proved to be cumbersome.

Modern technology has advanced considerably in providing apparatus tomonitor the progress of mothers in labor and the condition of the fetusduring labor. The process of vaginal birth may be assisted by hard steelforceps or a variety of available vacuum extraction devices. Althoughforceps are highly effective when used in the proper circumstances,vacuum extraction devices are less likely to cause maternal or infantinjury and can replace forceps in many cases.

Existing vacuum extractor devices include a variety of obstetric vacuumcups on the end of a handle combined with a hose attached to an externalvacuum source. The procedure for using the vacuum extractor is to draw avacuum on the cup only during uterine contractions. The vacuum cup isintended to hold on to the baby's head and to assist the birth byallowing the physician to pull on the baby's head as the mother pushes.Upon the cessation of each contraction, the vacuum is released until thenext contraction begins. The reasons for this procedure are well knownin the field and need not be discussed here.

The main problem with existing apparatus is the need for control of anexternal vacuum source. This requires either the physician's free handor a second person with coordinated action between the physician andthis second person. Additionally, the speed of response in drawing thevacuum is directly proportional to the volume and diameter of the hosesand ducts intermediate the vacuum cup and the vacuum pump. The greaterthe length of the tubes and the larger the diameter involved, the longerit will take to evacuate the system and produce the vacuum needed tosecure the cup to the baby's head.

It must be possible to repeatedly and quickly regenerate the vacuum forthese reasons:

1) Air leakage between the cup and the baby's head is common, reducingthe hold of the cup on the baby's head. This leakage is due to thebaby's hair, wires used for electronic fetal heartbeat monitoring, andpartial cup disengagement.

2) Fluids such as amniotic fluid, blood and vernix commonly enter thecup and occupy some space.

3) The vacuum is purposely interrupted between uterine contractions andmust be regenerated to enable the physician to pull and assist thebirth.

SUMMARY OF THE INVENTION

The inventive concept which will be described subsequently resulted in avacuum pump combined with a vacuum cup where the physician is incomplete control by hand manipulation of the degree of vacuum drawn onthe cup at all times and the whole process may be controlled andmanipulated by one hand while the physician's other hand performs anyother needed services during the process.

The uniqueness of this device is that its operation in all itsembodiments is performed through the natural squeezing motion of thehand. The squeezing motion of the human hand is its strongest and mostnatural action.

A valve system, either integral or detachable, can serve to maintain orrelease the vacuum. The same valve system allows exhaust of leakedfluids or air and regeneration of the vacuum.

As a result of the invention made specifically in relation toobstetrics, the structural features showed promise for use as a vacuumsyringe for withdrawing bodily fluids or performing biopsies of softtissues or solid organs by substituting a needle for the obstetricvacuum cup. A further concept allows a physician to use the same needleand vacuum apparatus to inject substances into a body using essentiallythe same structure using a one-handed squeezing motion to draw up thesubstance to be injected and with a return spring in the cylinder-pistoncombination to effect the injection stroke as an autoinjector.Alternatively, finger and thumb holes allow the physician to effect orassist the injection stroke. An additional further concept is to useboth the vacuum and injection features alternatively to create a pumpingaction to fill or evacuate body cavities or other vessels.

As to the obstetric vacuum cup invention, any particular cup currentlyavailable may be adapted to the use with the general apparatus of thisinvention which includes a piston and cylinder combination uniquelystructured to serve the desired purpose of the inventors. It includes aframe, an axially aligned piston and cylinder combination secured in theframe, and a closed loop secured to one side of the frame and extendingtherefrom to circumscribe a handle on the remote end of the piston andlooping around to be attached to the other side of the frame. The handleis configured such that the palm of the physician's hand may be locatedat the outer portion of the loop while the fingers of the same hand gripthe transversely extending handle and draw it toward the palm bysqueezing thereby creating a vacuum in the cylinder. This creates thenecessary vacuum on the obstetric cup in the conventional fashion. Acheck valve in line with the cylinder and cup acts to maintain thevacuum in the cup upon release of the handle. A vacuum gauge withappropriate indicia can be formed in the frame to allow the physician toobserve the degree of vacuum applied during the process if required.Thereby, when the desired degree of vacuum is achieved, the physicianmay release the piston handle and apply the pulling action to the looprather than continue to pull on the handle and draw too great a vacuumor if maximum vacuum is required, the physician may pull the handle andloop together, grasped within the hand.

A spring bias working between the loop and the outermost end of thepiston serves to drive the piston toward the innermost end of thecylinder in a return stroke. This return stroke serves to dischargeliquids or air from the cylinder which have been withdrawn during thevacuum application stroke. Such fluids are discharged through a sideduct. An exhaust valve mounted in the side duct opens during the returnstroke to allow the expulsion of any air or fluids that have entered thecylinder, thereby preparing for another squeeze of the operator's handto restore or increase the vacuum. Alternatively, finger holes in theframe adjacent to the cylinder permit a squeezing motion of the hand toapply a linear force to depress the piston to aid in exhausting leakedliquids or air from the cylinder. The size and structure of the exhaustport and various valves prevent them from being clogged by hair, vernix,blood or amniotic fluid, yet not leak air. The vacuum range of thedevice is up to about 600 mm HG or 11.6 lb/in².

A quick release of the vacuum in the cup upon the ending of acontraction is accomplished by opening a release valve. The release isspring biased to close a short passage in the frame, which passage leadsdirectly to the passage between the cup connection and the forwardmostend of the cylinder. The release valve is so located that the thumb ofthe physician may open it to allow air to rush into the vacuum throughthe short passage and relieve the vacuum almost instantaneously. Notethat this is still an one-handed instrument because of the location ofthe valve.

This same general structure may be used for extracting body fluids froma cavity, providing a needle biopsy of soft tissue or solid organs orproviding the controlled injection of fluids into a body cavity or bloodvessels. Medical procedures commonly applicable include:

Thoracentesis

Arthrocentesis

Paracentesis

Peritoneal lavage

Wound or eye irrigation

Percutaneous liver biopsy

Percutaneous kidney biopsy

Aspiration or biopsy of masses or tumors such as breast masses

Bone marrow aspiration

Chorionic villus sampling

Amniocentesis

Radiographically or sohographically-guided biopsies or aspiration

Drawing up into a syringe and subsequent injection of dyes or contrastagents for a variety of applications including angiograms, intravenouspyelography, choangiography, hysterosalpingography, fine needleaspiration and biopsy when fitted with a wider diameter flange, used toapply vacuum to skin for dermatologic applications such as cystevacuation or comedone extraction.

While the invention is described generally in relation to living animalsand not limited to humans, it will be clear that the device will beapplicable to evacuating gas or fluids from a cavity or vessel ortransferring gas or fluids from one cavity to another regardless ofwhether the cavities exist in a living organism.

If hoses are connected to the intake and exhaust ports, the device maybe used to transfer fluids from one vessel to another or simply tocreate a low volume, high pressure vacuum for other medical, laboratoryor industrial applications.

Objects of the invention not understood from the above, will be fullyappreciated upon a review of the drawings and a reading of theDescription of the Preferred Embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective, isometric, elevational view of the reproductiveportion of a human female showing a fetus in a normal birth position andwith the apparatus of the present invention secured to the head of thefetus;

FIG. 2 is a sectional view of a first embodiment of the extractor ofFIG. 1;

FIG. 3 is a sectional view of a second embodiment of the extractor;

FIG. 4 is a sectional view of a third embodiment of the extractor;

FIG. 5 is a sectional view of a fourth embodiment of the extractor;

FIG. 6 is a sectional view of a fifth embodiment of the invention wherethe apparatus includes a hollow needle at one end;

FIG. 7 is a sectional view of a sixth embodiment of the inventionsimilar in function to the FIG. 6 embodiment; and

FIG. 8 is a sectional view of a seventh embodiment of the inventionsimilar in function to the FIG. 6 embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is depicted a human female designatedgenerally at 10 in the position commonly assumed during child birth. Thefetus or infant designated generally at 12 is positioned in the birthcanal 14 with its head 16 in the normally downwardly directed position.The obstetrical delivery apparatus of the present invention designatedgenerally at 18 is gripped by the hand 20 of a physician.

Looking further at FIGS. 1-3, the delivery apparatus 18 includes a cup22 for fitting over the head 16 of the fetus, to grip the same andassist the physician in the birth process. The cup 22 is connected at 24by threads or other convenient means to one end of a frame 26. A piston28 and cylinder 30 combination are mounted in rigid operable position inthe frame whereby the piston 28 may reciprocate coaxially with thecylinder 30 as will explained in more detail subsequently.

A conventional seal element 32 is mounted on the forward end of thepiston 28 to provide a fluid tight seal between the piston and thesidewalls of the cylinder 30 to allow a vacuum to be drawn on the cup 22upon the retraction of the piston from the forward end of the cylinder.

The frame 26 includes a loop 34 projecting from one side of the frame tocircumscribe a transversely extending handle 36 on piston 28. Thepurpose of the handle 36 is to allow the fingers of the physician's hand20 to encircle the handle while the thumb rests on the remote portion 38of loop 34 as seen in FIG. 1.

A first passageway 40 extends from the inside of cup 22 through theforward portion of the framework 26 into fluid communication with theforward end of cylinder 30 to allow liquids or gases to be drawn fromcup 22 as it embraces the head of the fetus to draw a vacuum thereon andmaintain a secure connection allowing the physician to pull the head ofthe fetus partially through the birth canal upon the uterine contractionof the mother during the birthing process. A first check valve 42 isconfigured to allow the passage of fluid through passage 40 from cup 22into the cylinder upon the retraction of the piston 28. However, valve42 is oriented to prevent the reinjection of withdrawn fluids into thecup 22 upon the forward advance of the piston after the vacuum isreleased in cup 22 at the cessation of the contraction of the mother.

In order to expel the liquids and gases withdrawn through passage 40into cylinder 30 a second or exhaust passage or opening 44 is provided.Passageway 44 opens into passageway 40 and as the piston 28 reciprocatestoward the forward end of cylinder 30, check valve 42 closes and thefluids are forced to flow through second passage 44 which allows thedischarge of such fluids through a second check valve 46.

A third passageway 48 is formed in the frame to extend to the firstpassageway 40 intermediate the cup 22 and the check valve 42. Itsoutermost opening at a remote area of the frame is closed by a sealingvalve 50 having a thumb lever 52 which allows the physician to use histhumb to depress lever 52 and thereby lift valve 50 and open thirdpassageway 48 to the atmosphere. Opening valve 50 allows air from theatmosphere to flow through passages 48 and 40 into cup 22 and therebyrelieve the vacuum created by the retraction of piston 28 in cylinder30.

During the birthing process where the physician wishes to assist thefetus through the birth canal and the vacuum is drawn on cup 22, it isimportant that the optimum vacuum be drawn to minimize injuries to thefetus and maximize the ability of the doctor to give assistance at theright time. To achieve this desired result, a vacuum gauge 54 isprovided in the frame 26 in fluid communication with a fourth passageway56 which is in fluid communication with passage 40 and the forward endof cylinder 30.

In operation the physician folds the cup 22 which is very flexible toinsert it into the birth canal as illustrated in FIG. 1 and intoengagement with the head 16 of the fetus 12. Upon a uterine contractionthe physician may, using only one hand, draw a vacuum in cup 22 tosecure the head 16 to the framework 26 by using any of the embodimentsillustrated in FIGS. 2-5. This is accomplished by the fingers of thephysician gripping the underside of handle 36 while his thumb hooks overthe remote handle portion 38 of loop 34 and he squeezes to retract thepiston 28 from the forward end of the cylinder 30. Thereby gases andliquids are evacuated from the cup 22. Such fluids flow through passage40 and check valve 42 into cylinder 30. The squeezing continues untilthe desired vacuum is observed by the physician at the vacuum gauge 54.

At that point in time the squeezing can cease and the handle 36 may bereleased by the physician because the vacuum will remain. The physicianmay then pull to assist birth using the loop 34 for the pullingoperation.

Upon a release of the handle 36 by the physician's hand 20, the existingvacuum in cylinder 30 is relieved and the piston moves toward theforward end of the cylinder by itself or by (1) a spring bias 58 shownin FIG. 3, (2) a pair of elastomeric bands 60 as illustrated in FIG. 4or (3) the piston may be depressed by the hand of the physician usingfinger holes 62 and manually depressing the handle 36 by the thumb ofthe hand. Whatever mechanism moves the piston 28 to the forward end ofcylinder 30, the fluids drawn into cylinder 30 are expelled throughopening 44 because the check valve 42 seals the first passageway 40immediately upon the pressure in the cylinder exceeding the pressure incup 22 and second check valve 46 opens.

The check valve 46 allows the entrained fluids in cylinder 30 to exitthe frame 26 away from the birth canal and not be reinjected into itthrough passageway 40 and cup 22.

The point in time when the uterine contractions of the mother begin isthe time the physician wants to draw the vacuum as quickly as possibleto help the birth by pulling. That is something which the physician canobtain almost instantly in this invention by a squeezing of the handle36 and the remote portion 38 of the loop. The desired degree of vacuumcan be maintained during the contraction and the physician can pull asindicated previously until the contraction recedes. At that point intime it is important to relieve the vacuum on cup 22 and this isaccomplished by the thumb of the physician depressing valve lever 52 andlifting sealing valve 50 to allow atmospheric air to rush into the cup22 through passages 48 and 40. Thus, the vacuum in the cup is relievedfor the period of time when the uterine contraction is not taking place.As indicated previously, the reasons for this rhythmic procedure isknown in the art and it is not necessary to describe the same.

Note the locations of the sealing valve 50 in FIGS. 2-4 and thealternate location shown in FIG. 5. The particular location on the frameis not material to the operation of the apparatus so long as it iseasily and quickly accessible to the thumb of the physician.

FIG. 3 indicates a particular mechanism for maintaining axial alignmentbetween the piston and cylinder by providing a guide means 64 in theform of a rod extending coaxially with the piston through the handle andinto a bore 66 which is also coaxially aligned with the piston andcylinder combination.

FIG. 6 is a modification of the embodiments illustrated in FIGS. 1-5 inthat a hollow needle 68 is secured to the forward end of the frame 26 bya standard luer lock 70 in the conventional fashion. This particularembodiment could be used as a pump to withdraw a rather substantialamount of fluid or other material from a body cavity penetrated byneedle 68 in that the piston could be withdrawn and depressed aplurality of times to obtain the desired amount of material. Emptying offluid from the cylinder 30 can be accomplished manually by using fingerholes 62 and squeezing or automatically by biasing means 58 and 64. Anycommonly available tubing can be attached to exhaust port 44 where itopens into frame 26 for the purpose of collecting the fluid being pumpedout or to maintain a closed, sterile system if needed. With commonlyavailable adapters, the needle attached at 70 and collection tubingattached at 44 can be reversed permitting the device to be used to pumpfluids either in or out of a body cavity or other container. Medicalapplications include paracentesis, thoracentesis, peritoneal lavage ordialysis, etc. Laboratory and industrial applications include transferof fluids from one container into another. Varying the size of cylinder30 would determine the capacity of the stroke volume of the pumpingaction.

FIG. 7 is an alternate embodiment of FIG. 6 wherein the valves areabsent and indicia 72 are embossed on the exterior of cylinder 30 orotherwise incorporated such that a physician may observe the piston ashe withdraws it by squeezing the handle 36 and the remote part 38 of theloop until he has withdrawn the desired amount of fluid into cylinder 30following which biasing means 58 and 64 can effect the automaticinjection of this fluid into a body or vessel. This embodiment has manymedical applications including the automatic injection of medications,dyes, and contrast agents, as well as laboratory and industrialapplications.

FIG. 8 is a modification of the embodiments illustrated in FIGS. 6 and 7in that the biasing means 58 and 64 are absent. The needle may be usedto withdraw (aspirate) or inject fluids, or to perform biopsies oftissues such as liver, kidney, chorionic villus sampling, etc. whereinonce the needle penetrates the tissue, vacuum is generated by pullingthe handle 36 causing the tissue to enter the needle 68. Any currentlyavailable common needle or specialized biopsy needle may be fitted byluer lock at end 70 of frame 26. The sample obtained is contained in thecylinder 30 or retrieved from the needle lumen 68 in the fashioncommonly done in the field.

Having thus described the invention in its preferred embodiment, it willbe clear that modifications may be made without departing from thespirit of the invention. Also the language used to describe theinventive concept and the drawings accompanying the application toillustrate the same are not intended to be limiting on the invention.Rather it is intended that the invention be limited only by the scope ofthe appended claims.

We claim:
 1. A manually operable medical device comprising,means forminga cylinder with an axis, a medical tool attached to said cylinder means,said medical tool comprises a cup for attachment to the head of a fetus,means forming a duct leading from said medical tool to one end of saidcylinder means to provide fluid communication between said tool and saidone end of said cylinder means by way of said duct means, a pistonhaving an axis being mounted to reciprocate coaxially in said cylindermeans and configured to reciprocate in said cylinder means in responseto manually applied force to an end of said piston most remote from saidone end of said cylinder means, said piston including a handle at saidremote end, said handle extending transverse to said axes, a rigidclosed loop connected to said cylinder means and circumscribing saidhandle, said loop including a surface for palm contact by an operator ofsaid device upon said operator moving said piston to draw a vacuum insaid cylinder means by engagement of said handle by the fingers of saidoperator.
 2. The device of claim 1 including a first check valve in saidduct means, said first check valve being configured to prevent fluidflow from said cylinder means to said tool,means forming an opening fromsaid duct means, said opening means being located intermediate saidfirst check valve and said cylinder means, a second check valve meanslocated in said opening means and configured to allow fluid flow fromsaid cylinder means.
 3. The device of claim 2 including guide meanssecured to said loop for guiding the piston in its reciprocatingmovement.
 4. The device of claim 3 including a spring engaging said loopfor biasing said piston toward said one end of said cylinder means. 5.The device of claim 4 wherein said spring is a coil springcircumscribing said guide means.
 6. The device of claim 5 wherein saidguide means is a rod extending from said loop and coaxially aligned witha bore extending through said handle and into said piston, said borebeing coaxially aligned with said piston.
 7. The device of claim 6including indicia on at least one of said cylinder means and saidpiston, said indicia being configured to show one of (1) the volume ofthe cylinder means between said one end of said cylinder means and thepiston and (2) the degree of vacuum in said cylinder means.
 8. Thedevice of claim 3 wherein said guide means is a rod extending from saidloop and coaxially aligned with a bore extending through said handle andinto said piston, said bore being coaxially aligned with said piston. 9.The device of claim 1 including guide means secured to said loop forguiding the piston in its reciprocating movement.
 10. The device ofclaim 7 including a spring engaging said loop for biasing said pistontoward said one end of said cylinder means.
 11. The device of claim 10wherein said spring is a coil spring circumscribing said guide means.12. The device of claim 10 wherein said guide means is a rod extendingfrom said loop and coaxially aligned with a bore extending through saidhandle and into said piston, said bore being coaxially aligned with saidpiston.
 13. The device of claim 1 including a spring engaging said loopfor biasing said piston toward said one end of said cylinder means. 14.The device of claim 1 including a pair of finger sized openings in saidcylinder means to accommodate two fingers of an operator upon asqueezing of said handle by the operator's hand to urge said pistontoward said one end of said cylinder means.
 15. The device of claim 14including indicia on at least one of said cylinder means and saidpiston, said indicia being configured to show one of (1) the volume ofthe cylinder means between said one end of said cylinder means and thepiston and (2) the degree of vacuum in said cylinder means.
 16. Thedevice of claim 1 including a valve to open the cylinder means toatmospheric pressure to relieve the vacuum without moving said piston.17. The device of claim 16 including a first check valve in said ductmeans, said first check valve being configured to prevent fluid flowfrom said cylinder means to said tool,means forming an opening from saidduct means, said opening means being located intermediate said firstcheck valve and said cylinder means, a second check valve means locatedin said opening means and configured to allow fluid flow from saidcylinder means.
 18. The device of claim 17 including guide means securedto said loop for guiding the piston in its reciprocating movement. 19.The device of claim 18 including a spring engaging said loop for biasingsaid piston toward said one end of said cylinder means.
 20. The deviceof claim 19 wherein said spring is a coil spring circumscribing saidguide means.
 21. The device of claim 20 wherein said guide means is arod extending from said loop and coaxially aligned with a bore extendingthrough said handle and into said piston, said bore being coaxiallyaligned with said piston.
 22. The device of claim 16 including guidemeans secured to said loop for guiding the piston in its reciprocatingmovement.
 23. The device of claim 22 including a spring engaging saidloop for biasing said piston toward said one end of said cylinder means.24. The device of claim 23 wherein said spring is a coil springcircumscribing said guide means.
 25. The device of claim 24 wherein saidguide means is a rod extending from said loop and coaxially aligned witha bore extending through said handle and into said piston, and borebeing coaxially aligned with said piston.
 26. A manually operablemedical device comprising,means forming a cylinder with an axis, amedical tool attached to said cylinder means, means forming a ductleading from said medical tool to one end of said cylinder means toprovide fluid communication between said tool and said one end of saidcylinder means by way of said duct means, a piston having an axis beingmounted to reciprocate coaxially in said cylinder means and configuredto reciprocate in said cylinder means in response to manually appliedforce to an end of said piston most remote from said one end of saidcylinder means, said piston including a handle at said remote end, saidhandle extending transverse to said axes, a rigid closed loop connectedto said cylinder means and circumscribing said handle, said loopincluding a surface for palm contact by an operator of said device uponsaid operator moving said piston to draw a vacuum in said cylinder meansby engagement of said handle by the fingers of said operator, a firstcheck valve in said duct means, said first check valve being configuredto prevent fluid flow from said cylinder means to said tool, meansforming an opening from said duct means, said opening means beinglocated intermediate said first check valve and said cylinder means, asecond check valve means located in said opening means and configured toallow fluid flow from said cylinder means.
 27. A manually operablemedical device comprising,means forming a cylinder with an axis, amedical tool attached to said cylinder means, means forming a ductleading from said medical tool to one end of said cylinder means toprovide fluid communication between said tool and said one end of saidcylinder means by way of said duct means, a piston having an axis beingmounted to reciprocate coaxially in said cylinder means and configuredto reciprocate in said cylinder means in response to manually appliedforce to an end of said piston most remote from said one end of saidcylinder means, said piston including a handle at said remote end, saidhandle extending transverse to said axes, a rigid closed loop connectedto said cylinder means and circumscribing said handle, said loopincluding a surface for palm contact by an operator of said device uponsaid operator moving said piston to draw a vacuum in said cylinder meansby engagement of said handle by the fingers of said operator, a springengaging said loop for biasing said piston toward said one end of saidcylinder means.
 28. A manually operable medical device comprising,meansforming a cylinder with an axis, a medical tool attached to saidcylinder means, means forming a duct leading from said medical tool toone end of said cylinder means to provide fluid communication betweensaid tool and said one end of said cylinder means by way of said ductmeans, a piston having an axis being mounted to reciprocate coaxially insaid cylinder means and configured to reciprocate in said cylinder meansin response to manually applied force to an end of said piston mostremote from said one end of said cylinder means, said piston including ahandle at said remote end, said handle extending transverse to saidaxes, a rigid closed loop connected to said cylinder means andcircumscribing said handle, said loop including a surface for palmcontact by an operator of said device upon said operator moving saidpiston to draw a vacuum in said cylinder means by engagement of saidhandle by the fingers of said operator, a valve to open the duct meansto atmospheric pressure to relieve the vacuum without moving saidpiston.